The first top predators to walk on land were not afraid to bite off
more than they could chew, a University of Toronto, Mississauga study has
found. Graduate student and lead author Kirstin Brink and U of T Biology Professor
Robert Reisz suggest that Dimetrodon, a carnivore that walked on land
between 298 million and 272 million years ago, was the first terrestrial
vertebrate to develop serrated ziphodont teeth.

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According to the study published in Nature Communications,
ziphodont teeth, with their serrated edges, produced a more-efficient bite and
would have allowed Dimetrodon to eat prey much larger than itself.

While most meat-eating dinosaurs possessed ziphodont teeth, fossil
evidence suggests serrated teeth first evolved in Dimetrodon some 40
million years earlier than theropod dinosaurs.

"Technologies such as scanning electron microscope (SEM) and
histology allowed us to examine these teeth in detail to reveal previously
unknown patterns in the evolutionary history of Dimetrodon," Brink
said.

The four-meter-long Dimetrodon was the top of the terrestrial
food chain in the Early Permian Period and is considered to be the forerunner
of mammals.

According to Brink and Reisz's research, Dimetrodon had a
diversity of previously unknown tooth structures and were also the first
terrestrial vertebrate to develop cusps — teeth with raised points on the
crown, which are dominant in mammals.

The study also suggests ziphodont teeth were confined to later species
of Dimetrodon, indicating a gradual change in feeding habits.

"This research is an important step in reconstructing the
structure of ancient complex communities," Reisz said.

"Teeth tell us a lot more about the ecology of animals than just
looking at the skeleton."

"We already know from fossil evidence which animals existed at
that time but now with this type of research we are starting to piece together
how the members of these communities interacted."

Brink and Reisz studied the changes in Dimetrodon teeth across
25 million years of evolution.

The analysis indicated the changes in tooth structure occurred in the
absence of any significant evolution in skull morphology. This, Brink and Reisz
suggest, indicates a change in feeding style and trophic interactions.

"The steak knife configuration of these teeth and the
architecture of the skull suggest Dimetrodon was able to grab and rip
and dismember large prey," Reisz said.

"Teeth
fossils have attracted a lot of attention in dinosaurs but much less is known
about the animals that lived during this first chapter in terrestrial
evolution."